Motor vehicle audio system

Abstract

A motor vehicle audio system, and a method of operating such a system. There is at least one rear far-field speaker that is located behind a front seat of the motor vehicle, and at least one near-field speaker located in front of the far-field speaker and close to an intended position of a listener's head. There is an audio signal processor configured to detect when the rear far-field speaker is shut off while the near-field speaker remains on, and in response automatically increase the output energy of the near-field speaker.

What is claimed is: 
     
       1. A method of operating a motor vehicle audio system that has at least one rear far-field speaker that is located behind a front seat of the motor vehicle, and that also has at least one near-field speaker located in front of the far-field speaker and close to an intended position of a listener's head, the method comprising:
 detecting when the rear far-field speaker is shut off while the near-field speaker remains on; and in response 
 automatically increasing the output energy of the near-field speaker. 
 
     
     
       2. The method of  claim 1  wherein automatically increasing the output energy of the near-field speaker comprises operating the near-field speaker so as to at least partially replace the audio energy lost when the rear far-field speaker was shut off. 
     
     
       3. The method of  claim 2  wherein operating the near-field speaker so as to at least partially replace the audio energy lost when the rear far-field speaker was shut off comprises operating the near-field speaker so as to deliver approximately the same audio energy to the expected location of each ear of a front seat listener's position as was delivered before the far-field speaker was shut off. 
     
     
       4. The method of  claim 3  wherein operating the near-field speaker so as to deliver approximately the same audio energy to the expected location of each ear of a front seat listener's position as was delivered before the far-field speaker was shut off comprises adjusting an equalization of the near field speaker. 
     
     
       5. The method of  claim 1  wherein a transfer function from each far-field speaker that was shut off to the expected location of each ear of a front seat listener's position is known, and wherein automatically increasing the output energy of the near-field speaker comprises operating the near-field speaker so as to approximate the transfer functions from each far-field speaker that was shut off, to the expected location of each ear of a front seat listener's position. 
     
     
       6. The method of  claim 1  wherein the front seat of the motor vehicle comprises a driver headrest and a passenger headrest, and wherein the motor vehicle audio system comprises a pair of near-field speakers in each front seat headrest. 
     
     
       7. The method of  claim 6  wherein the motor vehicle audio system comprises a plurality of rear far-field speakers, and wherein automatically increasing the output energy of the near-field speaker comprises operating the pair of near-field speakers in a headrest so as to approximately replace the audio energy lost at the expected location of each ear of a front seat listener's position. 
     
     
       8. The method of  claim 1  wherein the motor vehicle audio system comprises a user-operated switch that is part of an audio head unit and that can be operated so as to shut off the far-field speaker. 
     
     
       9. A motor vehicle audio system, comprising:
 at least one rear far-field speaker that is located behind a front seat of the motor vehicle; 
 at least one near-field speaker located in front of the far-field speaker and close to an intended position of a listener's head; and 
 an audio signal processor configured to detect when the rear far-field speaker is shut off while the near-field speaker remains on, and in response automatically increase the output energy of the near-field speaker. 
 
     
     
       10. The system of  claim 9  wherein the audio signal processor automatically increases the output energy of the near-field speaker by operating the near-field speaker so as to at least partially replace the audio energy lost when the rear far-field speaker was shut off. 
     
     
       11. The system of  claim 10  wherein operating the near-field speaker so as to at least partially replace the audio energy lost when the rear far-field speaker was shut off comprises operating the near-field speaker so as to deliver approximately the same audio energy to the expected location of each ear of a front seat listener's position as was delivered before the far-field speaker was shut off. 
     
     
       12. The system of  claim 11  wherein operating the near-field speaker so as to deliver approximately the same audio energy to the expected location of each ear of a front seat listener's position as was delivered before the far-field speaker was shut off comprises adjusting an equalization of the near field speaker. 
     
     
       13. The system of  claim 9  wherein a transfer function from each far-field speaker that was shut off to the expected location of each ear of a front seat listener's position is known, and wherein the audio signal processor automatically increases the output energy of the near-field speaker by operating the near-field speaker so as to approximate the transfer functions from each far-field speaker that was shut off, to the expected location of each ear of a front seat listener's position. 
     
     
       14. The system of  claim 9  wherein the front seat of the motor vehicle comprises a driver headrest and a passenger headrest, and wherein the at least one near-field speaker comprises a pair of near-field speakers in each front seat headrest. 
     
     
       15. The system of  claim 14  wherein the at least one far-field speaker comprises a plurality of rear far-field speakers, and wherein the audio signal processor automatically increases the output energy of the near-field speaker by operating the pair of near-field speakers in a headrest so as to approximately replace the audio energy lost at the expected location of each ear of a front seat listener's position. 
     
     
       16. The system of  claim 9  further comprising a user-operated switch that is part of an audio head unit and that can be operated so as to shut off the far-field speaker.